1. Technical Field
The present invention relates to an axially adjustable cutting mechanism and, in particular, to an extrudate cutting mechanism that incorporates blade holders that can be adjusted for uniform contact with an extruder die face.
2. Description of Related Art
Extruders used in the food processing industry commonly employ cutting devices that cut extrudate to a desired size as it exits the die face of the extruder. An example of prior art cutting mechanisms used with an extruder is shown in FIGS. 1, 2, and 3.
FIG. 1 shows a side view of a tube turn 110, bell 112, and die 114 assembly of an extruder. In operation, product, such as masa, is forced through the tube turn 110 into the bell 112. It is then extruded through the die 114. A shaft 116 extends through the turn 110, bell 112, and die 114. Mounted on the end of the shaft 116 is a cutting mechanism. The cutting mechanism comprises a hub 130, spokes 132 extending from the hub 130, and blade holders 134 attached to the spokes. Each blade holders 134 in turn maintains a blade 136 in contact with the die 114.
FIG. 2 shows a bottom view of the die face 115. Corresponding reference numerals are used to represent corresponding elements on all figures unless otherwise indicated. The die face 115 will typically exhibit a number of channels or ports 120 that are cut through the die 114, thus allowing communication of the product from the bell, through the die 114, onto the die face 115. As the product emerges from these ports, it is cut into relatively uniform pieces by the blades 136 as the entire cutting mechanism rotates about the shaft in the direction 102 illustrated in FIG. 2. Such rotation 102 is typically in speeds ranging from sixty to one hundred fifty rpm, with approximately one hundred forty rpm generally used for cutting masa extrudate.
FIG. 3 shows a perspective view of a prior art cutting mechanism detached from the extruder. The side of the cutting mechanism presented is the same side that interfaces with the die face. Again shown is the hub 130, the spokes 132, the blade holders 134, the blades 136, and the direction 102 of intended rotation. The blade holders 134 on a prior art cutting mechanism are rigidly mounted to the spokes 132, and thus static in relation to the cutting mechanism. Consequently, referring back to FIG. 1, the distance between the die face 115 and the blades 136 cannot be easily adjusted for each individual blade 136. The overall distance of the cutting mechanism from the die face 115 is adjusted by using washers placed between the hub 130 and the die face 115. The casting tolerance of the entire mechanism is relied upon to insure a consistent contact between each individual blade 136 and the die face 115. However, if a spoke 132 or blade holder 134 becomes slightly bent or is otherwise out of tolerance, the blades 136 will not make consistent contact with the die face 115. This can result in uneven cutting or smearing of the extrudate and misshapen product.
Exact tolerance between the blades 136 and the die face 115 is particularly important when the extrudate shape is complex, such as the race car shaped extrudate that would be generated by the die 114 shown in FIG. 2. This race car pattern of the die ports 120 requires that the blades 136 remain consistently flush against the die face 115 and not deflect away from the die face 115 during cutting. Attempts to maintain consistent tolerance between the blades 136 and die face 115 in the past using prior art cutting mechanisms include physically bending the blade holders 134 or spokes 132. This was not found to be an acceptable solution for the application shown in FIG. 2, however. Regardless of the minor adjustments made to the cutting mechanism, a consistent and clean cut, with no smearing of the extrudate pieces or misshapen product, could not be consistently achieved with the prior art cutting mechanism.
Consequently, a need exists for a cutting mechanism that is adjustable such that the fit between the cutting blades and the die face can be maintained consistently and adjusted as required. Such adjustable cutting mechanism should be adaptable to existing extruders and provide for clean cuts through extrudate even when the extrudate involves complex shapes.